Bituminous emulsions



Patented Sept. 5, 1950 UNITED STATES PATEN BITUMINOUS aMonslons Walter JSchwarz, New Orleans, La., assignor to The Patent and LicensingCorporation, New York, N. Y., a corporation of Massachusetts No Drawing.Application March 20, 1947,

' Serial No. 736,111

7 Claimss (01.252-3115) V This invention relates to aqueous emulsions:of bituminous substances, such as asphalts, pitches, waxes and the like,and more particularly to emulsions of such substances made by the use ofwater swellable clays such as bentonite, as the emulsifying agent.

Bituminous emulsions of the type above referred to are well knownandhave been employed for various industrial purposes. These emulsions, asnormally manufactured, are composed, for example, in the case of asphaltemul-'- sions, of from approximately 45 to 60 of asphalt,

2 to 3% of bentonite as the emulsifying agent and 38 to 52% of water,depending upon the softening point and other physical properties of theasphalt and upon the technique employed to bring about emulsificationthereof. Generally speaking, the asphalt is emulsified by heating thesame to a temperature substantially above its softening point andfeeding it while in moltenv state and at a, predetermined temperature tosuitable emulsifying apparatus, concurrently with the feeding thereto ofan aqueous suspension or slip of the bentonite. The emulsifyingapparatus is provided with agitating blades of suitable design so thatin the operation the liquefied asphalt becomes dispersed or emulsifiedin the aqueous phase by forces of attenuation and interfacialtrituration, the emulsified particles being held in suspension in theaqueous phase and prevented from coalescing therein by the adsorbedfilmsof water and bentonite. 5

Depending mainly upon the'character .of the asphalt and the amount ofwater employed in the manufacture, asphalt emulsions of the type:

above described are of rather viscous, sometimes pasty, consistency whendischarged from the Since the water is in the external phase, theseemulsions can be thinemulsifying apparatus.

ned by dilution with water but this means of reducing the viscosity ofthe emulsions is undesirable, especially where the emulsions are to beshipped over any considerable distance from the point of theirmanufacture to the point of their use. It is known that the fluidity ofthese emulsions may be increased withoutincreasing the water contentthereof, by subjecting the emulsion to a beating action, as described,for example, in the patent to Kirschbraun No. 1,616,904. The amount ofthinning action that may be effected by such beating treatment however,of a limited order. Furthermore, even when thus ,thlnned, theseemulsions. exhibit a strong tendency.

the material at the point of use. Frequently, the

emulsions became gelled to an extent such that allic acid, when employedj 1 m d salts are employed insuitableproportio they donot havesufiicient fluidity to enable themto be discharged from bung-type drumsorother; containers in which theyareshipped. i-; 1' The principal objectofthe invention isto pro,-, vide emulsions of the general characteraboveindicated, having, however, considerably higher fluidity than isnormally characteristic thereof without materially increasing the watercontent-i More specifically, it is an object of theinvention to provideemulsions of this character, which}, will retain the higher degree offluidity, over-rel-f atively long periods of time during which the,product may be in storage or shipment; V .1 In thepatent to-KirschbraunNo. 1,918,759, it..- is proposed to convert the relativelythick short-g bodied consistency of bituminous emulsions madej withbentonite as the emulsifying agentinto-a; relatively thin long-bodiedconsistency, by treats; ing them with small quantities of certain g-or-zganic acids. Although certain of the acidsregi ferred to in that patenthave been found to be eifective for that purpose, the viscositydepressgj ing effect thereof in most instances isiprimarilya an initialeffect which doesnot endure'for a substantial period oftime, theemulsion revertinggto'i a substantiallythickened or non-fluidcondition;' within relatively: short periods. of time, especiallyrelatively'small quantities. of water soluble; all-4.:

kaline sal-ts'of certain organic acids, :ashereina after to be moreparticularly set forth,'the amount of the salt employed for this purposebeing gov I erned largely by the initial viscositycof theemule 3;; sion,and the degree and permanence of viscosity depressing effect desired. I

More specifically 1 have found, that th kaline salts, and preferably thesodium salts, such acids as tannic acid, gallic acid and, pyro amounts,of the order of from 0.05% .to 0,,5 by weight of the emulsion,- areeffectivefor-bring-s; ing about-a very marked reduction inthe; viscosityofthe emulsion... Moreover, when'these;

viscosity of the emulsion ;will not. materially in crease overconsiderable periods of time, say o;- the orderof30 to daysfl 1- In the.case of sodium tannateQthefam n thereof may, vary from 0,06%to.0,2%iby:we ghts, of the emulsion; with sodium gallate the amount 9employed may vary from 0.05% to 0.5% by weight of the emulsion; and whenemploying sodium pyrogallate, the amount may vary from 0.05% to 0.30% byweight of the emulsion.

Thus by my invention it becomes possible, for example, to producebituminous emulsions containing as high as 57% to 60% of dispersedbitumen, but having a fluidity comparable to or higher than that of anemulsion containing 45% to 58% of the same bitumen, as normally madewithout the treatment embodying the invention.

Preferably, the treatment of the emulsion with the selected salt iseffected in the presence of a small excess of free alkali, as may beobtained by reacting sodium hydroxide with the corresponding organicacid in an amount in excess of that required to react with all theavailable carboxyl and hydroxyl groups of the acid. I have found thatthe provision of such excess alkali inhibits progressive gelation andconsequent thickening of the emulsion which might otherwise result fromelectrolytic action when the emulsion is stored or shipped in metalcontainers. The amount of excess alkali for this purpose is such as toimpart to the treated emulsion a pH value within the range ofapproximately 7.8 to 12.0.

In terms of actual measurement, the fluidity of the emulsions hereinreferred to is reflected by the readings in centipoises taken on aBrookfleld viscosimeter at temperatures of 77-85 F. From the practicalstandpoint, the emulsions are considered to possess a fluiditysatisfactory for handling if Brookfield viscosity value thereof is lessthan about 7000 centipoises. Preferably, however, the viscosity shouldnot exceed 4500 centipoises. These values are the average of thecentipoise readings taken with the spindle of the Brookfieldviscosimeter rotating at speeds of 6, 12, 30 and 60 R. P. M., and whenthe readings have come to equilibrium (usually after about five minutes)In referring to the fact that the emulsions produced in accordance withthe invention do not undergo material increase of viscosity duringstorage for a stated period of time, it is meant that the viscosity atthe end of the -period of storage will nevertheless be within the rangeof values above indicated, though the viscosity may be higher than whenmeasured at the beginning of the storage period. In this sense, thefluidity of the emulsion may be considered as virtually unchanged, foralthough the numerical rise in ccntipoise viscosity reading may behigher at the end of the storage period than at its beginning, theproduct is as fluid for handling after the storage period as at itsoutset. In other instances, the viscosity at the end of the storageperiod may be even lower than at the outset.

The treatment of the emulsion according to the invention is preferablyperformed by incorporating the selected treating salt in the emulsionwhen the latter is at a substantialiy lower temperature than that atwhich it is discharged from the emulsifying apparatus. The temperatureof the emulsion at the time of treatment may be from normal atmosphericto about 135 F.

Preferably, the required amount of the selected salt is added to theemulsion in the form of a concentrated solution thereof in water,usually not-less than a 10% solution, in order that the amount ofadditional water thereby added to the emulsion shall be as little aspossible. The solution of the salt is preferably incorporated in theemulsion in successive increments while the 4 emulsion is stirred oragitated, although in certain instances it may be desirable toincorporate a portion of the solution, constituting in some cases only aminor portion thereof, in the manner above indicated, the balance beingadded to the thus treated emulsion after it has been delivered to astorage tank.

The following are specific examples, illustrating the practice of theinvention:

Example I This example illustrates the invention as applied for thetreatment of an emulsion of asphalt of relatively high softening pointasphalt, say to F., and having relatively high solids content. (i. e.,relatively low water content). Asphalt having a softening point ofapproximately 185 F., and 0 penetration (at 77 F.), is emulsified inwater, with bentonite clay as the emulsifying agent. The emulsificationis carried on -so as to produce a base emulsion having substantially thefollowing composition, in parts by weight:

Asphalt 54.5 Bentom'te 2.5 Water 43 As normally produced, this emulsionis of a heavy paste consistency (far too heavy to permit of taking aviscosity reading on the Brookfield, the maximum reading on which is100,000 centipoises) and its pH value is approximately 6.5.

In 99.8 parts of the above emulsion there is incorporated 0.2 part ofsodium tannate (solids, by weight, based on the total emulsion) composedof equal parts by weight (solid basis) of sodium hydroxide and tannicacid in a 10% aqueous solution. This solution is added to the emulsionin successive increments, the emulsion being preferably agitated duringthe addition of at least the first several increments of the treatingsolution. By this treatment, although the water content has beenincreased only to approximately 43.6% from the. original water contentof 43.0%, the heavy paste or buttery consistency of the base emulsionistransformed to a fluidity of the order reflected by a viscosity ofapprorimateiy 1820 centipoises. After a storage period of fifty days,the emulsion thus treated retained its fluid ity, exhibiting, if anychange in this respect, a thinner: consistency than at the beginning ofthe storage period, as reflected by a viscosity of the order of '860centipoises.

It will be noted that in this example, sodium tannate was made .up ofequal par-ts by weight of sodium hydroxide and tannnic acid. Tannic acidhaving a molecular weight of 322.2..and sodium hydroxide having amolecular weightof 40.,

it will be seen that equal parts :by weight is equivalent to 8 moles ofsodium hydroxide to 1 mole of tannic acid, or an excess :of 2 moles :of

sodium hydroxideover the alkali required to react with all the available(six). hydroxyl groups of the tannic acid. In terms .of excess .alkali,this amounts to 0.026% freealkali, based on the total weight of theemulsion, resulting in a .pH value of 1.1.6.

Example If In this example, a similar base emulsion as referred to inExample I is treated with the same quantity of sodium tannate' as inExample I,. but in this instance the sodium tanna'te was made up of 1part of tannic acid and 0.75 part of so-, dium hydroxide (solids weightbasis), in solution in 2 parts water. It will be seen, therefore, that75 in this example, the sodium tannate is made up of one mole of theacid and six moles orthe alkali, i. e., the amount of alkali used wasthe amount required to react with all the available (six) hydroxylgroups of the tannic acid, and no free alkali was, therefore, present.The thus treated emulsion had a pH of 8.9.

The result of this treatment upon the base emulsion was to transform itsinitial heavy paste consistency into a fluid condition of the orderindicated by a viscosity of approximately 19,000 oentipoises. Althoughthe viscosity depressing efiect was thus less than in the treatment inaccordance with Example I, the treated emulsion of this exampleexhibited a suflicient thinning out trend, so that at the end of astorage period of approximately seventy days, the viscosity wasapproximately 4300 centipoises. From a practical point of view, theemulsion thus treated is fluid enough to be discharged from a bungtypedrum, though not as fluid as is usually desirable for shipment in thistype of container.

Example III In this example, 99.8 parts, by weight, of the same baseemulsion as referred to in Example II, is treated with 0.2 part (byweight solids based on the total emulsion) of sodium tannate composed of3 parts of sodium hydroxide (solid basis) and 1 part tannic acid (solidbasis), in a 20% aqueous solution. It will be noted that the sodiumtannate used in this example contained 18 moles of excess sodiumhydroxide; in terms of free alkali, this amounts to 0.112% free sodiumhydroxide by weight, based on the total emulsion. The pH value of thetreated emulsion was 11.6. With the sodium tannate of this example, theheavy paste condition of the base emulsion was transformed to a fluidcondition reflected by viscosity reading of 1720 centipoises. Thefluidity remained substantially unaltered during a storage period ofninety-five days, at which time it exhibited, if any change in thisrespect, a slight decrease in viscosity, via, to .1620 centipoises.

Example IV In this example, the invention is illustrated with referenceto an emulsion of an asphalt of substantially the same softening pointas that in the previous examples, but the base emulsion as initiallyproduced having a substantially higher water content than the baseemulsion of the previous examples.

The base emulsion was made so as to have substantially the followingcomposition, in parts by weight:

Asphalt (softening point 185 F.; penetra- The emulsion thus producedpossesses a fluidity reflected by a viscosity of approximately 17,000centipoises, and exhibits a tendency to gel to somewhat non-fluidcondition in storage.

99.94% parts by weight of the emulsion was treated with 0.06 part byweight of sodium tannate made up of equal parts. by weight .(solidbasis) of tannic acid and sodium hydroxide. This is equivalent, as inthe case of Example I, to a ratio of 1 mole tannic acid to 8 molessodium hydroxide. The sodium tannate was employed in a 20% aqueoussolution. This treatment re sulted in a sizeable initial reduction inviscosity (to approximately 2000 centipoises) with a slight trend tothinning out during storage, so that at the end of a; Period oftwenty-two days-storage, the viscosity of the emulsionwas approximately1450 centipoises. p 4 f Example V In this instance, the treatment inaccordance with the invention was appliedto'a'n- 'e'mulsionof an asphalthaving a softening point of 110*to 120 F., i. e., a considerably lowersoftening point than that referred to in the previous. examples, theemulsion, however, having .a water content approximately the same as thebase emulsions .in Example I, II and III. Steam refined asphalt havingasoftening point of approximately 112 F., and a penetration of 85 to 100at 77 emulsified with bentonite. as the emulsifying-agent, toproducea-base. emulsionhaving substantially the following composi- Thisbase emulsion has a pH value of approximately 7.2 and a fluidity such asreflected by a viscosityof' 23,000 centipoises. I weight of this baseemulsion'was treated "with 0.1 part by weight of'sodium tannate composedof 1 part tannic acidand 0.75 part sodium hy-g droxide (solids basis).In other words, the so dium' tannate was made up of one'mole of thetannic acid and six moles of sodium hydroxide. The pH of the treatedemulsion was 9.5. The effect of this treatment was to 'depress thevisf-Q cosity to a value of approximately 3500 new tipoises, thisviscosity remaining substantially.

unaltered during a storageperiod of thirty-two days. Example VI 99.94parts by weight of the same baseemul-vv sion as referred to in ExampleV, was treated with 0.06 part by weightof sodium tannate composed ofequal parts by weight of sodium hydroxide and tannic acid.- Thus,in-this instance,

the sodium tannate was made up in a molar ratio of 8 moles of sodiumhydroxide to1i=1 mole-of tannic acid, or an excess of 2 moles of sodiumhydroxide over the alkali needed to react with the available hydroxylgroups.

Under these conditions, the. treatment of the. emulsion with thesodiumtannate depressedtheg viscosity of the emulsion to substantiallythe;

same extent, namely, to a-viscosity of aboute3500 centipoises, as.in thecase of the sodium tannate employed inExampleV. However, whereas in.thecase of Example V there was no material; change of a viscosity after'a storage period .01; thirty-two days, the viscosity of the emulsion,

treated according to this example increasedsome what, viz., toapproximately 6700 -centip0ises, whenstoredfor thirty-twd days. 1 Fromthis. standpoint, therefore, the treatment according to Example V may beconsidered asproviding a better over-all effect for thisbaseemuleionthan does the treatment of this example,

Erample j l I resulted in depressing the viscosity of the base 99.9partsfby 7 amal am emulsion toa viscosity of the-order: of 1 200centipoises. After a thirty-two day storage period, the viscosityincreased only slightly. Thus, the treatment according to thisexamplemay be considered more efiective for this base emulsion than either ofthetreatments described in Examples V and Example VIII ,In this example,there-is illustrated the use of sodium pyrogallateas the viscositydepressing agent.

In this instance, 99.8 parts of a base emulsion of 185 Fymelt pointasphalt having a water content of'46;0% were-treated with 0.2% part 1 byweight of sodium pyrogallate made by-reacting sodium hydroxide withpyrogallic acid in proportions toprovide a mole ratio of 1 mole oftheacid to 3 moles of the hydroxide. This treatment resulted in depressingthe viscosity of the base emulsion from a paste consistency toapproximately '11'00 centipoises. The pH of this emulsion was 10.1.

Example IX In this example, there is illustrated the use of sodium.gallate as the viscosity depressant.

"In this instance 99.94 parts of a base emulsion of 185 F. melt pointasphalt having a water content of 500% were treated with 0.06 part byweight of sodium gallate, made by reacting 1 mole gallic acid with'4moles sodium hydroxide. (Thebase emulsionhad been stored for aconsiderable'time and in spite of the high water content had gelled topaste consistency.) The treatnient resulted'in depressing the viscosityfrom a p,

paste consistency to approximately 1200 centipoises. The pH of thisemulsion was'7.8.

I claim:

1. A bituminous emulsion consisting essentially of approximatelyato 60%.bitumen-asthe'disperse phase, approximately 1.5 to 3% bentonite astheemulsifying agent and water :as thecontinuousphase, and containingapproximately 0.95 to :0.5%mby:weight-of analkali-metal salt of norganicacid selected-from the group consisting of tannic acid, =.gallic.acid and :pyrogallic acid, the amount of said salt being sufiicientfltoimpart to the qemulsionua viscosity.substantiallyclower than it normallypossessesinxthe absence of said salt.

2. A bituminous :emulsion consisting essentiallyof approximately45.to60% bitumen as the disperse phase,.approximately 1.5 to 3%bentonite as theemulsifying agent and water as-the'continuouslphase,and: containing approximately 0.05

to- 0.5% by weighto'f an alkali metal salt of 'an organic acid selectedI from the group consisting of tannic acid, gallic acid and pyrogallicacid, theam'ount-of said salt beingsufiicient to impart to -'theemulsion a viscosity substantially lowerthan it normally possessesin'the absence of said-salt, and a-n amount of free alkali to impart tothe emulsion'a pI-I valuewithin'the range of 758 to 12.0.

3. A bituminous emulsion consisting essentially of approximately 45m 60%of bitumen as the disperse phase, approximately 1.5 to 3% bentonite asthe emulsifying agent and water as the continuous phase, and containingapproximately 0.05 to 0.5% by weight of an alkali metal salt of anorganicacid selected 'from the group consisting of tannic acid, gallicacidand pyrogallic acid, said emulsion being characterized by an initialviscosity and a viscosity after storage for -'a period of notlessthandays,substantiallylower'than 8 thein-itial viscosity andthe;Viscosityaftersuch storage period,of-saidemulsion in the absence ofsaid salt.

4. A bituminous emulsion consisting essentially of approximately to--%-bitumen as'the disperse phase, approximately 1.5 to 3% bentonite asthe-emulsifying agent and water as the continuous phase,and-"containing0.06% 110-0.2% of sodium tannate, said-emulsion beingcharacterized by an initial viscosity-and a viscosity after storage fora period ofnot lessthan 20"days,'substantially lower than the-initialviscosity and the viscosity after such storage period, of said'emulsionin the absence of said sodium tannate.

5. A bituminous emulsion consisting-essentially of 'approximately45to60% of bitumen as-the disperse phase, approximately 1 .5 to 3% bentoniteas theemulsifying agent-and -water as the continuous phase, said'bitumen having a softening point of approximately 1 to 185F., saidemulsion containing 0.06 to 0.2% by weightof sodium tannate, saidemulsion being characterized by an initial viscosity and a viscosityafter storage fora periodpfnot less'than'20days, substantially lowerthan the initial viscosity and'the' viscosity after such storage-period,of'said'emulsion in the absenceof said sodium tann'ate.

6. A bituminous emulsionconsisting essentially of approximately '45-to60% of bitumen as the disperse phase approximately 1.5 to' 3 bentoniteas the emulsifying'agent and wateras the continuous pliase,said bitumenhaving a softening-point of approximately to "F., said emulsioncontaining-0.05m 0.5% by weight of sodium gallate, said emulsion beingcharacterized by an initial viscosity and a "viscosity after storagefora period of not less than 20 days,'substantially lower than-theinitial viscosity and the viscosity aftersuch storage period, of saidemulsion in the absence of said sodium gallate. 7

1. A bituminous-emulsion consisting essentially of approximately 45 to60% of bitumen asthe disperse phase, approximately 1.5to 3% ofbentoniteas the emulsifying agent and water as the continuous phase, andcontaining 0.05 to 0.3% by weight of sodium pyrogallate, said emulsionbeing characterized by an initial viscosity anda viscosity after storagefor a period of not less than 20 days, substantially lower than theinitial viscosity and the viscosity after :such storage period, of saidemulsion in the absence of .said sodium pyrogallate.

WALTERJ. SCHWARZ.

REFERENCES CITED The following references are of .record in the,

file of this patent:

UNITED STATES .I-ZATENTS .Number Name Date 1,918,759 Kirschbraun July18, 1933 1,963,231 Fain June 19, 193.4 1,995,346 Halvorsen Mar..26, 19352,380,156 Dobson JulyllO, 1945 FOREIGN PATENTS Number Country Date246,907 Great Britain Feb. 3, 1926 350,744 Great Britain June 18, 1931OTHER REFERENCES Role of Clay and Other ,Minerals in Oil Well DrillingFluids. Report of Investigation by.

Bureau of Mines. .Feb. 1941; R. I. 3556, p. '68.

(Copyin Division 64.)

1. A BITUMINOUS EMULSION CONSISTING ESSENTIALLY OF APPROXIMATELY 45 TO60% BITUMEN AS THE DISPERSE PHASE, APPROXIMATELY 1.5 TO 3% BENTONITE ASTHE EMULSIFYING AGENT AND WATER AS THE CONTINUOUS PHASE, AND CONTAININGAPPROXIMATELY 0.05 TO 0.5% BY WEIGHT OF AN ALKALI METAL SALT OF ANORGANIC ACID SELECTED FROM THE GROUP CONSISTING OF TANNIC ACID, GALLICACID AND PYROGALLIC ACID, THE AMOUNT OF SAID SALT BEING SUFFICIENT TOIMPART TO THE EMULSION A VISCOSITY SUBSTANTIALLY LOWER THAN IT NORMALLYPOSESSES IN THE ABSENCE OF SAID SALT.